The present invention relates to an apparatus for applying polymer resin materials to threaded fasteners, and more particularly, to an apparatus for mechanically handling and orienting a small threaded fastener to properly position it for application of the resin to an internally threaded bore located in a cylindrical body of the fastener.
It is common practice today in the fastener industry to apply various polymer resins to threaded fasteners. Among the most common practices is the application of a resilient polymer, typically nylon, to the fastener""s threads to provide a self-locking function. Such fasteners, when assembled with another complementary threaded element, are resistant to loosening due to vibration or other external forces. In order to economically produce these self-locking fasteners, it is essential that the application of the polymer resin be accomplished by means of automated equipment, with production rates oftentimes in the range of thousands of pieces per hour. Such automated apparatus and processes, in turn, typically require some form of mechanical handling and part orientation equipment to ensure the proper placement of the resin to the desired threads of the fastener.
When the fastener involved is relatively small and comprises an internally threaded element, the problem of proper part orientation can be more difficult. In the case where the part is asymmetrical, this problem can be further exacerbated.
The present invention represents an efficient and cost effective solution to the problem of properly positioning a small threaded fastener having a cylindrical body with internal threads extending along a bore in the body, where the bore extends diametrically across the body along an axis generally perpendicular to the axis of the body.
The present invention is directed to an apparatus for the application of a polymer resin to a threaded fastener, where the fastener includes a cylindrical body and the threads of the fastener are formed in a bore extending diametrically across the body. The apparatus generally comprises a conveyor, a resin application station and a fastener orientation station. The conveyor carries the fasteners along a predetermined path of travel, and includes one or more fastener support members that permit the individual fasteners to rotate about the axes of their cylindrical bodies. The application station comprises a nozzle which directs a stream of the resin toward the travel path of the fasteners. The orientation station includes a guide member which operates to rotate each of the fasteners relative to the conveyor as they move toward the application station, and to thereby properly orient the fasteners so the threaded bore of each fastener will intersect the resin stream as the conveyor carries the fasteners along the travel path and through the spray station.
In one preferred embodiment, the guide member of the orientation station comprises a resilient guide surface which is biased toward the travel path of the fasteners and is shaped to complement the configuration of the travel path. In this way, as each of the fasteners carried by the conveyor enters the orientation station, the circumference of its cylindrical body engages the guide surface causing the fastener to rotate. However, the bore which extends through the cylindrical body forms an interruption in the circumference of the body. As a result, the fastener will rotate as it passes along the surface of the guide member, but will stop rotating and remain rotationally stationary when the interruption on the fastener""s circumference is juxtaposed with the guide surface. In this way, each fastener exiting the orientation station is properly positioned for receipt of the resin stream as it subsequently enters the application station.